Casing Patch and Seal

ABSTRACT

A casing patch assembly may include a patch seal having two ring-type seals with different performance characteristics. A first ring seals against a casing patch and a casing stub. A second ring self-adjusts to the size of the casing stub and is located so that it blocks the first seal, which may be softer material than the second ring, from being squeezed into an annular gap between the casing patch and the casing stub. The second ring may include a split feature to allow for the self-adjustment. Optionally, a third ring made of a malleable material may be located between the first and second rings to protect the first ring from being damaged by movement of the split feature.

FIELD OF THE INVENTION

This invention relates generally to a patch for a well casing and, more particularly, to a seal for a casing patch.

BACKGROUND OF THE INVENTION

Casings for wells often require maintenance and repair which involves installation of a patch at a segment of the casing. Various means for patching a well casing are known, such as those described in U.S. Pat. No. 5,829,524 to Flanders et al., entitled High Pressure Casing Patch, and U.S. Pat. No. 4,660,863 to Bailey et al., entitled Casing Patch Seal, both of which are incorporated herein by reference.

A casing patch can be a tube of a certain length that is positioned at the area requiring repair due to perforation in or other damage to an existing well casing, which is also referred to as a casing string. Casing patches are installed outside and surround the well casing. The casing patch must be sealed onto the existing well casing to prevent gases, liquids, or other material from flowing into and/or out of the casing string.

The seals may include what are known as packers, which can have various configurations depending on the type of casing patch, the pressure levels inside and/or outside the casing, the type of material flowing in the casing during well operations, and other factors. The seal can be a ring of elastomeric material placed between the casing patch and the existing well casing. The ring is often required to change in diameter from a non-installed state, while the casing patch and ring are moved down in the well, to an installed state in which the casing patch and seal are coupled onto the existing well casing. A metal spring can be imbedded inside the ring to strengthen the ring and/or facilitate an appropriate change in diameter.

Many prior art seals are incapable of withstanding high pressures, such as pressures above 7,000 psi (48,000 kPa). The seals, which are often soft and malleable to allow for a change in diameter and to ensure good contact with the casing, can extrude into the gap between the casing patch and existing casing due to pressure and/or become damaged by surrounding metal parts to such an extent that the seal leaks or fails. Accordingly, there is a need for casing patches that can operate at high pressures and seals resistant to extrusion and/or damage due to high pressures.

SUMMARY OF THE INVENTION

Briefly and in general terms, the present invention is directed to a casing patch assembly, seal, and method of sealing a casing patch onto a casing stub.

In aspects of the present invention, a casing patch seal comprises a first part adapted to provide a seal between an inner tube and an outer tube surrounding the inner tube, and a second part adapted to cover a circular gap between the inner tube and a constricted portion of the outer tube and to prevent the first part from entering the gap. In further aspects, the first part is configured to expand after replacement of the inner tube with another inner tube having an outer diameter that is less than that of the replaced inner tube.

In other aspects, a casing patch seal comprises a first ring adapted to maintain sealing contact with an outer tube and a first inner tube inside the outer tube, and a second ring adapted to block the first ring from moving axially into a gap between the first inner tube and the outer tube. In detailed aspects, the second ring is configured to change in circumference after replacement of the first inner tube with a second inner tube having a different diameter than the first inner tube. In further aspects, the seal further comprises a third ring disposed adjacent to the second ring, the third ring adapted to deform against the second ring.

A casing patch seal in other aspects of the present invention comprises a seal ring adapted to seal a casing stub to a casing patch bowl, and a non-extrusion ring adapted to block the seal ring from moving axially into a gap between the casing stub and the casing patch bowl. In detailed aspects, the non-extrusion ring includes a split feature and two ends at the split feature, the two ends adapted to move relative to each other to allow the non-extrusion ring to change in circumference.

In aspects of the present invention, a casing patch assembly comprises a casing patch, a protector sleeve axially movable relative to the casing patch, and a seal disposed between the casing patch and the protector sleeve. The seal includes a seal ring and a blocking ring adapted to block movement of the seal ring in an axial direction relative to the casing patch. In detailed aspects, the seal further includes a protector ring disposed between the seal ring and the blocking ring, the protector ring adapted to deform after a change in shape of the blocking ring.

In other aspects of the present invention, a method of sealing a casing patch to a casing stub comprises sealing the casing patch to a casing stub with a sealing ring, and covering a gap between the casing patch and the casing stub with a blocking ring that blocks a sealing ring from moving into the gap. In further aspects, the method also includes replacing a protector sleeve disposed adjacent to the sealing ring with the casing stub, and after the replacement of the protector sleeve, allowing or inducing the blocking ring to change in circumference in accordance with a circumference of the casing stub.

The features and advantages of the invention will be more readily understood from the following detailed description which should be read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is cross-sectional view of a patch assembly, showing a casing patch before it is installed onto an existing well casing.

FIG. 2 is a partial cross-sectional, detail view of a seal region of the patch assembly of FIG. 1, showing four patch seals inside separate grooves formed into a casing patch, two of the seals oriented in one sealing direction and the other two seals oriented in the opposite sealing direction.

FIG. 3 is a partial cross-sectional, detail view of a locking region of the patch assembly of FIG. 1, showing a grapple and bowl subassembly adapted to engage a top segment of an existing well casing.

FIG. 4 is a cross-sectional, detail view of a patch seal, showing three separate ring components disposed between two tubes, such as a seal protector and the casing patch.

FIG. 5 is a cross-sectional view of the seal region of FIG. 4 after the patch assembly has been coupled onto another tube, such as an existing well casing.

FIG. 6 is perspective view of a ring, showing two overlapping, tapered ends of the ring at a split feature for allowing the ring to change in diameter and circumference.

FIG. 7 is perspective view of a segment of the ring of FIG. 6 after the ring has changed in diameter and circumference, showing a change in shape as a result of movement of the tapered ends relative to each other.

FIG. 8 is an elevation view of a segment of a patch seal, showing three seal members disposed immediately adjacent to one another, a non-extrusion ring having a split feature, a seal protector ring conforming to the split feature, and a seal ring protected from damage from the split feature by seal protector ring, the non-extrusion ring filling an enlarged annulus created by the casing stub with a smaller outside diameter and thereby further protecting the seal ring.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now in more detail to the exemplary drawings for purposes of illustrating embodiments of the invention, wherein like reference numerals designate corresponding or like elements among the several views, there is shown in FIG. 1 a cylindrical patch assembly 10 before it is placed into a well. The patch assembly is capable of engaging and sealing off a properly prepared casing string in an existing well. When installed, the patch assembly surrounds an outer surface of a casing stub, which is an end segment of the existing casing, and remains in place so as to become part of the casing string that continues up toward the surface of the well.

It will be appreciated that patch seals of the present invention are not limited to patch assemblies that surround an outer surface of an existing well casing. Patch seals of the present invention may be implemented with casing patches that are installed inside an existing well casing.

Referring again to FIG. 1, a tubular top sub 12 is connected to a tubular extension sub 14, which is connected to a tubular casing patch bowl 16, and a tubular guide 21 is connected to the bottom of the tubular casing patch bowl. A circular bore extends entirely through the top sub 12, the extension sub 14, the casing patch bowl 16, and the guide 21 which may be connected to each other by mating threads or by interlocking features known in the art. Various seals at the connection areas may also be used to prevent leakage into and out of the casing string. In other embodiments, the patch assembly has no extension sub, and the top sub 12 is connected directly to the casing patch bowl 16.

As shown in FIGS. 1 and 2, a packer segment 18 of the patch assembly 10 includes the casing patch bowl 16, multiple packers or patch seals 20, and a tubular seal protector sleeve 22. Each of the patch seals 20 are disposed inside separate grooves 24 formed into an inner surface of the casing patch bowl 16. The opening of the grooves 24 and the patch seals 20 are covered by an outer surface of the protector sleeve 22. The protector sleeve is temporarily maintained in its axial position by shear pins 28 or other engagement devices configured to release the protector sleeve when a force axially applied to the protector sleeve exceeds a threshold level.

As used herein, the term “axial” refers to a line, orientation, or direction that is parallel or substantially parallel to a central axis 26 running through the middle of the patch assembly 10 or axis of some other circular structure. The term “radial” refers to a line, orientation, or direction that is perpendicular or substantially perpendicular to the central axis 26 or axis of some other circular structure.

In use, a casing stub, i.e., the top end of an existing well casing, abuts the bottom end 25 of the protector sleeve 22. As the patch assembly 10 is pushed downward onto the casing stub, the shear pins 28 release the protector sleeve 22 to allow the sleeve to move axially upward toward the top sub 12. The patch seals 20 remain in the grooves 24 as the protector sleeve 22 moves upward. The casing stub (not shown in FIGS. 1 & 2) moves into position adjacent to the patch seals 20, which seal against the casing stub. Preferably, the protector sleeve 22 is pushed upward by the casing stub until the protector sleeve abuts a lip or ledge 30 (FIG. 1) formed in the inner surface of the top sub 12.

As shown in FIG. 2, each of the grooves 24 in the casing patch bowl 16 have a sloped end surface 27 and a flat end surface 29 at opposite ends of the groove. The sloped end surfaces 27 form narrowing or constricted portions of the casing patch bowl 16. Each of the sloped end surfaces 27 form an acute angle 31 relative to the opening of the groove 24 and are oriented in such a way to allow a portion of the patch seals 20 to wedge tightly into a gap located adjacent to the sloped surface and between the casing patch bowl 16 and a casing stub.

Whether the sloped end surface 27 is located axially above or below the flat end surface 29 defines the predominant sealing direction of the patch seal 20 inside the groove 24. Where the sloped end surface 27 is located axially above the flat end surface 29, such as in grooves 24 a and 24 c, the respective patch seal 20 a, 20 c prevents gases, liquids, and/or other materials outside of the casing string from leaking into the casing string. Where the sloped end surface 27 is located below the flat end surface 29, such as in grooves 24 b and 24 d, the respective patch seal 20 b, 20 d prevents gases, liquids, and/or other materials inside the casing string from leaking out of the casing string.

In the illustrated embodiment of FIGS. 1 and 2, each of the grooves 24 extend completely around in a circle inside the casing patch bowl 16. The patch seals 20 are ring-shaped and extend continuously around the entire circumference of the grooves 24.

It will be appreciated that any number and combination of grooves 24, patch seals 20, and sealing directions may be implemented in a patch assembly of the present invention. In other embodiments, a patch assembly includes a fewer or a greater number of patch seals 20 than what is shown in FIGS. 1 and 2. In some embodiments, all the patch seals and grooves are oriented in the same sealing direction.

Referring now to FIGS. 1 and 3, a segment of the patch assembly 10, referred to as a grapple segment 32, is located below the packer segment 18. The bowl 16 is hollow and carries a grapple 34 which is adapted to move axially relative to the bowl 16, though the amount of movement is limited. An interior surface of the bowl 16 includes a helical catch feature 36 that spirals around the inside diameter of the bowl. The catch feature 36 include tapered slip surfaces 38 that face axially upward toward the top of the well when installed. There is also a catch surface 40 that faces axially downward toward the bottom of the well when installed. The catch surface 40 spirals around the inside diameter of the bowl 16. The catch feature 36 is shaped to match and engage the outer surface of the grapple 34. A grapple control 23 prevents rotational movement of the grapple 34 relative to the bowl 16.

As shown in FIG. 3, the interior surface of the grapple 34 includes spiraling, wickered features or sharp, radially inward facing threads 35 configured to engage a top segment of an existing well casing, referred to as a casing stub. In use, the grapple 34 is rotated relative to the casing stub, which enters inside the grapple 34 and engages the spiral feature or wickered threads 35 of the grapple. The threads 35 are shaped to allow one-way movement of the casing stub in an axially upward direction toward the packer segment 18 (FIG. 1). The catch features 36 of the bowl 16 prevent the grapple 34 from moving upward along with the casing stub. After the patch assembly 10 has been completely lowered onto the casing stub, such as when the casing stub has entered the grapple 34 and pushed the protector sleeve 22 up against the ledge 30 of the top sub 12, the patch assembly can be pulled upward so that the slip surfaces 38 of the segment 32 push the outer surface 42 of the grapple 34 in a radially inward direction, which causes the threads 35 to lock onto the casing stub.

In the illustrated embodiment of FIGS. 1 and 3, the segment 32 containing the grapple 34 is an integral continuation of the tube forming the casing patch bowl 16. In other embodiments, the segment 32 can be a separate tubular section that is connected to the casing patch bowl 16.

It will be appreciated that locking subassemblies other than the bowl and grapple shown in FIGS. 1 and 3 may be implemented in a patch assembly of the present invention.

In some embodiments, the casing patch has an inner diameter between about 14 inches (35.6 cm) and 15 inches (38 cm). The patch seal may have an inner diameter of 13.75 inches (35 cm) and an outer diameter of about 14.75 inches (37.5 cm). It is not intended that the invention be limited to the foregoing dimensions. It will be appreciated that smaller and/or larger dimensions may be implemented in other embodiments of the present invention.

Referring next to FIG. 4, a patch seal 50 is shown between a cylindrical wall of an inner tube 52 and a cylindrical wall of an outer tube 54. The cylindrical walls are concentric or substantially concentric with each other and extend completely around a central axis 55. The inner tube 52 is disposed inside a central bore of the outer tube 54.

In some embodiments, the inner tube 52 is a protector sleeve and the outer tube 54 is a casing patch, such as described, for example, in connection with FIGS. 1 and 2 above.

The patch seal 50 in FIG. 4 is disposed in an annular slot or groove 56 formed into the outer tube 54.

Referring again to FIG. 4, the patch seal 50 provides a means for sealing the inner tube 52 and outer tube 54 to each other. The patch seal 50 includes a first part 58 that seals against the inner tube 52 while simultaneously sealing against the outer tube 54. The first part 58 is disposed adjacent to a non-beveled portion 62 of the groove in the outer tube 54. A second part 60 is disposed adjacent to a beveled portion 64 of the groove in the outer tube 54. The first and second parts 58, 60 are capable of moving independently of each other. The first and second parts 58, 60 extend in a circle around the central axis 55 so as to form rings between the inner and outer tubes 52, 54. The inner diameter, D1, of the outer tube 54 at the beveled portion 64 is smaller than the inner diameter, D2, of the outer tube 54 at the non-beveled portion 62.

The first part 58 can be formed of a resilient material that is softer than the material of the second part 60. The resilient material preferably has sufficient resiliency and compliance so as to allow the first part 58 to compress and/or expand in response to a change in the size of the space occupied by first part between the inner and outer tubes 52, 54. In some embodiments, the first part 58 is made of an elastomeric material or elastic polymer and the second part 60 is made of a metal. A suitable elastomeric material is rubber, though it will be appreciated that other elastomeric materials may be implemented. A suitable metal for the second part 60 is steel, though it will be appreciated that other metals and alloys may be implemented.

As used herein, “compliance” of a material refers to the ability or tendency of the material to stretch, expand, or deform in response to some external force or pressure. As used herein, “resiliency” of a material refers to the ability or tendency of the material to return to a rest state or non-deformed state after removal or a reduction in the external force or pressure.

In FIG. 5, the inner tube 52 of FIG. 4 has been replaced by another inner tube 66. The replaced inner tube 52 of FIG. 4 has an outer diameter, D3, that is larger than the outer diameter, D4, of the new inner tube 66 as it pushes the inner tube 52 away from the seals and replaces the inner tube 52. In response to the change from D3 to D4 and the application of pressure, the first part 58 has expanded to seal against the new inner tube 66. An inner surface 68 of the first part 58 has moved apart from an outer surface 70 which remains sealed against the outer tube 54. Also, the second part 60 has contracted in circumference in response to the change from D3 to D4 and the application of pressure. In some embodiments, the new inner tube 66 is a casing stub.

Referring again to FIG. 5, a slot 71 extends around the entire circumference of the first part 58. In some embodiments, the slot may facilitate expansion of the first part 58. In further embodiments, a spring (not shown) is imbedded inside the slot 71 to urge the first part 58 to seal against the new inner tube 66. In other embodiments, the first part 58 has no slot.

Referring once again to FIG. 5, the beveled portion 64 of the outer tube 54 includes a bevel surface 72 that extends around in a circle so as to form conical surface shape. The second part 60 includes a bevel surface 74 having a shape that corresponds to the bevel surface 72 of the outer tube 54. The corresponding shapes of the bevel surfaces 72, 74 allow the second part 60 to axially move further into the beveled portion 64. The second part 60 also includes an inner contact surface 76 that defines an inner diameter of the second part 60 which has reduced in size in response to the change from the inner tube diameter D3 (FIG. 4) to D4 (FIG. 5). The second part 60 is preferably made of a material having a hardness and strength sufficient to prevent the second part from being extruded through a gap 75 between the new inner tube 66 and the beveled portion 64 of the outer tube 54. In this way, the second part 60 blocks or prevents the first part 58, which may in some embodiments be softer than the second part 60 to facilitate a sealing function, from moving axially into the gap 75 due to pressure inside or outside of the casing string.

Referring to FIGS. 4 and 5, a medial or third part 78 is disposed axially between and in contact with the first and second parts 58, 60. The third part 78 is capable of moving independently of the first and second parts 58, 60. The third part extends in a circle around the central axis 55 so as to form a ring. The third part 78 includes top and bottom surfaces that are oriented to correspond with the orientation of the respective surfaces of the first and second parts 58, 60. In the illustrated embodiment of FIGS. 4 and 5, the bottom surface is substantially perpendicular to the central axis 55 and the top surface is conically sloped. The sloped top surface may facilitate movement of the first member 58 towards the new inner tube 66 when a pressure increase or other force that pushes the first member axially toward the beveled end of the groove 56.

In other embodiments, the top and bottom surfaces of the third part 78 may have other orientations. For example, both the top and bottom surfaces may be substantially perpendicular to the central axis 55.

In further embodiments of the present invention, the second part 60 of the patch seal 50 is in the form of or includes one or more split rings capable of changing in diameter and circumference.

In FIGS. 6 and 7, a split ring 80 for use in a casing patch seal is shown in two configurations. The split ring has two opposing, tapered ends 82, 84 that meet at a split feature 86. The ends are opposing in a sense that they have surfaces that face toward each other. The split feature 86 includes a cut 88 that extends entirely through the split ring 80. The ends 82, 84 are capable of moving relative to each other to allow the split ring 80 to change in diameter. Going from FIG. 6 to FIG. 7, the ends 82, 84 have moved circumferentially toward each other in circumferential directions 92, 94, causing the split ring 80 to reduce in diameter. Going from FIG. 7 to FIG. 6, the ends 82, 84 have moved circumferentially away from each other in circumferential directions 96, 98, causing the split ring 80 to increase in diameter.

In some embodiments, the split ring 80 functions like a spring and is biased to have the configuration shown in FIG. 7. That is, the split ring 80 is capable of returning automatically from the configuration shown in FIG. 6 to that shown in FIG. 7. In this way, the split ring 80 may self-adjust radially inwardly onto a casing stub or other structure surrounded by the split ring. In other embodiments, the split ring 80 is biased to have the configuration shown in FIG. 6, wherein the split ring returns automatically from the configuration shown in FIG. 7 to that shown in FIG. 6. In this way, the split ring 80 may self-adjust radially outwardly to a structure that surrounds the split ring.

In some embodiments, the split ring 80 may be implemented in a patch seal such that when a patch assembly is being moved into position prior to engaging a casing stub, the split ring has a starting, non-installed configuration as shown in FIG. 6 when coupled to a protector sleeve. In the starting configuration, a contact surface 99 faces the protector sleeve and the ends 82, 84 of the split ring are aligned so as to form a planar circular edge 100. As used herein, a circular edge is “planar” when all points on the edge lie on a common plane. When the protector sleeve is replaced by a casing stub having a smaller diameter, the split ring 80 moves to an installed configuration as shown in FIG. 7. In the installed configuration, the contact surface 99 contacts the casing stub and the ends 82, 84 form a non-planar circular edge 102. As used herein, a circular edge is “non-planar” when all points on the edge do not lie on a common plane.

In other embodiments, the split ring 80 has a starting, non-installed configuration in which the ends 82, 84 of the split ring are spaced apart from each other. In the installed configuration on a casing stub having a smaller diameter, the ends 82, 84 of the split ring may move circumferentially relative to each other to the positions shown in FIG. 6 and form a planar edge 100. In situations where the casing stub is even smaller, the ends 82, 84 of the split ring may move further to the positions shown in FIG. 7 and form a non-planar edge 102 when in the installed configuration.

The split or cut 88 is at an oblique angle to the central axis 90. As used herein, “oblique angle” refers to an angle between one degree and eighty-nine degrees. The oblique orientation of the cut 88 allows the ends 82, 84 to overlap each other. The oblique orientation also allows opposing slip surfaces 104, 106 at the overlapping ends to slide against each other during changes in diameter and circumference.

Referring next to FIG. 8, a patch seal 110 in accordance with an embodiment of the present invention includes a ring seal 112, a protector ring 114, and a blocking ring 116. Applicants have found that the patch seal configuration shown in FIG. 8 can withstand pressures at or around 18,500 psi (over 127,000 kpa). The ring seal 112 may be used to seal a casing stub to a casing patch. The blocking ring 116 may be used to prevent the ring seal from moving axially into a gap between the casting stub and casing patch. The ring seal 112 may be made of a softer material than the other seal components so as to be sufficiently resilient and compliant for sealing against a casing stub. Suitable materials for the ring seal 112 include without limitation, plastic, rubber, elastomers, and swelling elastomers.

Swelling elastomers are polymeric materials that expand upon contact with an activating agent and may include a cross-linked polymer that swells multiple times from its initial size upon activation. The activating agent may be a wellbore fluid, water-based fluid, hydraulic fluid, or other fluid. It will be appreciated that swelling elastomers known in the art and others may be implemented.

The blocking ring includes a split feature 118 that allows the blocking ring to adjust in circumference to match a casing stub. In some instances, tapered ends 120 of the blocking ring slide above and below each other during the change in circumference to an extent in which tips 122 of the tapered ends become exposed or protrude. The blocking ring 116 may be made of a harder material than the ring seal 112 so as to be sufficiently resistant to being squeezed or extruded through a gap between the casing stub and casing patch. Suitable materials for the blocking ring 116 include without limitation, steel, stainless steel, and other metal alloys.

The protector ring 114 is disposed between the ring seal 112 and the blocking ring 116 and may be used to protect the ring seal 112 from being damaged by the exposed tips 122 of the blocking ring. The protector ring 114 may be made of the same material used for the ring seal 112. The protector ring 114 may also be made of a material that is intermediate in hardness to the ring seal 112 and the blocking ring 116. The protector ring 114 may be made of a malleable material so that it can deform at a region adjacent to the split feature 118. Deformation can be induced by swelling of the ring seal 112 and/or an increase pressure. The protector ring 114 is preferably of sufficient hardness so that the deformation results in relatively smooth surfaces and edges as compared to the exposed tips 122. In this way, the ring seal 112 is isolated from the blocking ring 116 and damage to the ring seal at a region above the split feature 118 is avoided. Suitable materials of the protector ring 114 include without limitation, lead, plastic, elastomers, and swelling elastomers.

While several particular forms of the invention have been illustrated and described, it will also be apparent that various modifications can be made without departing from the scope of the invention. For example, a patch seal may include a ring seal immediately above a blocking ring with no protector ring disposed in between. It is also contemplated that various combinations or subcombinations of the specific features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the invention. Although some of the embodiments have been described in connection with well casings, it will be appreciated that the assemblies and seals of the present invention may be used with other types of tubular casings, such as for example high pressure industrial pipes and other hollow conduits and containers. Accordingly, it is not intended that the invention be limited, except as by the appended claims. 

1. A casing patch seal comprising: a first part adapted to provide a seal between an inner tube and an outer tube surrounding the inner tube; and a second part adapted to cover a circular gap between the inner tube and a constricted portion of the outer tube and to prevent the first part from entering the gap.
 2. The seal of claim 1, wherein the first part is formed of a softer material than that of the second part.
 3. The seal of claim 1, wherein the first part is configured to expand after replacement of the inner tube with another inner tube having an outer diameter that is less than that of the replaced inner tube.
 4. The seal of claim 1, wherein the first part includes an inner sealing surface defining a seal diameter, the sealing surface adapted to seal around the inner tube, and wherein the first part is formed of a resilient material that allows the seal diameter to change in size.
 5. The seal of claim 1, wherein the first part is a ring including an inner surface for contacting the inner tube and an outer surface for contacting the outer tube, and wherein the inner and outer surfaces are adapted to move apart from each other to maintain sealing function after replacement of the inner tube with another inner tube having an outer diameter that is less than that of the replaced inner tube.
 6. The seal of claim 1, wherein the second part is formed of a metal.
 7. The seal of claim 1, wherein the second part is configured to contract in circumference after replacement of the inner tube with another inner tube having an outer diameter that is less than that of the replaced inner tube.
 8. The seal of claim 1, wherein the second part includes an inner contact surface defining a contact diameter, and a cut extends through the second part to allow the contact diameter to change in size.
 9. The seal of claim 1, wherein the second part is a ring including two opposing ends adapted to move relative to each other to allow the ring to change in circumference.
 10. The seal of claim 9, wherein the ends include tapered portions of the ring.
 11. The seal of claim 9, wherein the ends overlap each other.
 12. The seal of claim 1, further comprising a third part disposed between the first and second parts.
 13. The seal of claim 12, wherein the third part is formed of a material softer than that of the second part to allow the third part to at least partially conform to an adjacent surface feature of the second part.
 14. The seal of claim 12, wherein the third part is formed of a material harder than that of the first part.
 15. The seal of claim 12, wherein the third part is formed of a material including lead.
 16. A casing patch seal comprising: a first ring adapted to maintain sealing contact with an outer tube and a first inner tube inside the outer tube; and a second ring adapted to block the first ring from moving axially into a gap between the first inner tube and the outer tube.
 17. The seal of claim 16, wherein the second ring is configured to change in circumference after replacement of the first inner tube with a second inner tube having a different diameter than the first inner tube.
 18. The seal of claim 16, further comprising a lead ring disposed between the first and second rings, the lead ring having a hardness greater than that of the first ring and lower than that of the second ring.
 19. The seal of claim 16, further comprising a third ring disposed adjacent to the second ring, the third ring adapted to deform against the second ring.
 20. The seal of claim 16, wherein the second ring is a split ring.
 21. The seal of claim 20, wherein the split ring includes end portions that overlap each other.
 22. The seal of claim 20, wherein a split in the split ring is at an oblique angle to the central axis of the split ring.
 23. The seal of claim 20, further comprising a third ring disposed immediately adjacent to the split ring and adapted to deform at opposing ends of the spit ring.
 24. A casing patch seal comprising: a seal ring adapted to seal a casing stub to a casing patch bowl; and a non-extrusion ring adapted to block the seal ring from moving axially into a gap between the casing stub and the casing patch bowl.
 25. The seal of claim 24, further including a protector ring disposed between the seal ring and the non-extrusion ring, the protector ring adapted to at least partially conform to an adjacent edge of the non-extrusion ring.
 26. The seal of claim 24, wherein the non-extrusion ring includes a contact surface movable from a first configuration for facing a protector sleeve to a second configuration for facing the casing stub.
 27. The seal of claim 26, wherein the contact surface has a diameter when in the first configuration that is smaller than when in the second configuration.
 28. The seal of claim 26, wherein the contact surfaces includes a circular edge, the circular edge being substantially planar when the contact surface is in the first configuration and substantially non-planar when the contact surface is in the second configuration.
 29. The seal of claim 28, further comprising a protector ring adjacent to the circular edge, the protector ring adapted to at least partially conform to the circular edge.
 30. The seal of claim 24, wherein the non-extrusion ring includes a split feature and two ends at the split feature, the two ends adapted to move relative to each other to allow the non-extrusion ring to change in circumference.
 31. The seal of claim 30, further including a protector ring adjacent to the non-extrusion ring, the protector ring adapted to deform after the relative movement of the two ends of the non-extrusion ring.
 32. A casing patch assembly comprising: a casing patch; a protector sleeve axially movable relative to the casing patch; and a seal disposed between the casing patch and the protector sleeve, the seal including a seal ring and a blocking ring adapted to block movement of the seal ring in an axial direction relative to the casing patch.
 33. The assembly of claim 32, wherein the protector sleeve is axially movable relative the seal to allow placement of a casing stub adjacent to the seal.
 34. The assembly of claim 33, wherein the blocking ring is adapted to change in circumference after placement of the casing stub adjacent to the seal.
 35. The assembly of claim 32, wherein the seal further includes a protector ring disposed between the seal ring and the blocking ring, the protector ring adapted to deform after a change in shape of the blocking ring.
 36. A method of sealing a casing patch to a casing stub, the method comprising: sealing the casing patch to a casing stub with a sealing ring; and covering a gap between the casing patch and the casing stub with a blocking ring that blocks a sealing ring from moving into the gap.
 37. The method of claim 36, further comprising allowing or inducing a change in shape of the blocking ring.
 38. The method of claim 37, further comprising protecting the sealing ring from damage after the change in shape.
 39. The method of claim 36, further comprising: replacing a protector sleeve disposed adjacent to the sealing ring with the casing stub; and after the replacement of the protector sleeve, allowing or inducing the blocking ring to change in circumference in accordance with a circumference of the casing stub.
 40. The method of claim 39, further comprising allowing or inducing a protector ring disposed between the sealing ring and blocking ring to deform after the change in circumference of the blocking ring. 